Woods was in visible pain trying to pick up his tee and later at his car in the parking lot, where in brief remarks he said he "jarred it" when he jumped into a fairway bunker on the second hole after hitting a shot from an awkward stance.
The 14-time major winner was in distress at his car as he attempted to take off his golf shoes and change into tennis shoes. He could barely stand, bracing himself at the back of the vehicle, unable to tie his shoes.
"It happened on the second hole when I hit my second shot, I fell back into the bunker," Woods said. "I just jarred it, and it's been spasming ever since."
The stance outside of the bunker was an awkward one, as he basically swung off his right leg -- the ball too close to the bunker to take a regular stance. He fell back into the steep bunker and then ran to the bottom, and while he didn't show much discomfort at the time, his caddie, Joe LaCava, said Woods was hurting the rest of the way.
"He did a good job of masking it," LaCava said.
Woods hit several poor shots at the fifth, sixth and seventh holes, playing them in 3 over. He parred the 8th, then hit a 315-yard drive at the ninth but could barely bend over to pick up his tee. He then summoned a golf cart and had difficulty sitting in it.
Woods had surgery on March 31 to alleviate a pinched nerve in his back following just four tournaments in 2014. He withdrew from the Honda Classic during the final round and then played the WGC-Cadillac Championship the next week, shooting a third-round 66 but finding himself in distress during a final-round 78.
According to Woods' agent, Mark Steinberg, Woods is "back in Florida, [for] evaluation and then treatment."
Playing partner Bubba Watson didn't see Woods hit his shot on the second hole but knew something was amiss as he played poorly over the rest of the front nine.
"He hit some shots that we're not used to seeing Tiger hit, even when he's coming back from an injury like this," Watson said. "We don't see shots like that.
"So obviously, something was bothering him, and so you could kind of tell something was going on, and then when he hit the shot [on the ninth hole], hit the draw, he probably wasn't trying to play a draw on 9, and when he came over it like that, his back probably tightened up and caused the draw.
"Again, like I told him when I shook his hand, I said, 'I'm praying for you. Hope everything turns out good. Hope to see you next week.'"
In several interviews since the surgery, Woods said that the pain he felt in his back prior to the surgery left him wondering about his future in golf.
"I couldn't get out of bed," he said.
That pain went away following the surgery called a microdiscectomy, Woods said, and he had reported no issues with his back until Sunday.
Woods returned earlier than expected in June at the Quicken Loans National at Congressional Country Club, where he missed the cut. After an opening-round 69 at the Open Championship, Woods faltered and finished 69th, his worst 72-hole finish in a major as a pro.
This was his third tournament back on a Firestone Country Club course where he has won eight times. He opened the tournament with a 68 but got progressively worse and was 3-over par for his round when he withdrew Sunday.
"It's just the whole lower back, I don't know what happened," he said.
Woods' status for the PGA Championship this week in Louisville, in which he is scheduled to play, is unclear.
"I don't know," he said. "Just trying to get out of here."
Phil Mickelson, who is scheduled to play with Woods in the first two rounds of the PGA Championship, saw Woods struggling on the ninth hole while he was playing the 11th.
"It didn't look good," Mickelson said. "It looked like he was really in pain. I hope he's OK. I mean, I hope he's able to play next week. I hope it's a muscle and nothing serious because I'm really looking forward to playing with him. We rarely get paired together. If we do, it's been early Saturday.
"So it's nice to be paired together and have a couple of rounds and I hope he's able to play it. As much as I love playing with him, playing against him, trying to beat him, it's we all want him in the field. We all want him back. I just hope he's OK."
Tiger On Back Injury
Tiger Woods discusses the back injury he suffered that caused him to withdraw from the WGC-Bridgestone Invitational.